Risk of psoriasis according to body mass index: A retrospective cohort analysis.

BACKGROUND:Psoriasis has been linked to obesity, although data on the incidence of psoriasis according to body mass index (BMI) are limited. OBJECTIVE:To compare incidence of psoriasis among patients stratified by BMI category (normal or underweight, overweight, obese class 1, obese class 2/3). METHODS:Retrospective cohort analysis of a demographically heterogeneous sample of over 1.5 million patients in the United States between January 1, 2008 and September 9, 2019. RESULTS:Crude incidence of psoriasis per 10,000 person-years was 9.5 (95% confidence interval [CI], 9.1-10.0) among normal or underweight patients, 11.9 (95% CI, 11.4-12.4) among overweight patients, 14.2 (95% CI, 13.6-14.9) among obese class 1 patients, and 17.4 (95% CI, 16.6-18.2) among obese class 2/3 patients. Compared to patients with BMI < 25.0, those who were overweight (adjusted hazard ratio, 1.19; 95% CI, 1.12-1.27; P < .001), obese class 1 (adjusted hazard ratio, 1.43; CI, 1.34-1.53; P < .001) and obese class 2/3 (adjusted hazard ratio, 1.83; CI, 1.71-1.95; P < .001) significantly greater risks for developing psoriasis. LIMITATIONS:Influence of obesity on psoriasis severity could not be measured. CONCLUSION:BMI independently influences the development of psoriasis. There appears to be a graded association between BMI and risk of psoriasis.